Abstract »Acousto-Ultrasonic Structural Health Monitoring (SHM) of plate-like structures, such as for example composite fuselage, using sparse arrays of glued piezo-electrical sensors has extensively been reported. This family of techniques based on the generation and detection of guided waves by a sparse array of sensors glued to the structure relies on the comparison of the signals acquired on the structure during or after operational loading with baseline signals acquired on the pristine structure.
This paper investigates an alternative mode of operation of the Acousto-Ultrasonic technique made possible when the sparse array is not permanently glued to the structure but relies on probes designed to generate in direct and quasi-dry contact mainly low frequency flexural modes. The use of portable sparse array potentially allows to image the integrity of a zone of the structure delimited by the elements of the array. Damage detection and location can then be performed through a comparison with a baseline matrix of signal acquired on a similar pristine reference part. Imaging of the zone under inspection is performed using tomographic reconstruction similar to the procedure used for SHM application.
The performances of a sixteen channel system including an innovative concept for reconfigurable sparse-array that can be modified to adapt to the geometry of the structure under inspection is discussed. Imaging of typical damage type (impact delamination, disbond,etc..) in typical geometries (plates, T stringers and hat profiles) and materials (CFRP, bonded aluminum) is presented . Other potential applications such as the instantaneously screening for delamination around drill holes is also discussed.
The proposed technique, which relies on principles originally developed for SHM applications, shows good potentials for addressing some of the limitations associated with classical NDT procedures such as ultrasonic scanning. In particular, the technique opens for fast inspection of small components of complex geometry (such as brackets), can potentially reduce the inspection time for large structures through patch imaging and in certain application be used as a screening technique using a go/no go criteria.

Authors

Biography:Christophe Mattei is a doctor within Physical Acoustics with 20 years experiences in the fields of Ultrasonics and material characterization. After his doctoral studies at the university of Denis Diderot, he performed post-doctoral studies at The Ohio State University. He then joined the industry in Sweden, developping techniques and equipment for NDT and SHM applications. He is now leading the \"Smart Structures\" group at Creo Dynamics AB, a SME located in Sweden and providing specialist services within aerodynamics, Acoustics and Smart Structures.www.creodynamics.com